Romans
King James Version (KJV)

“That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.”
King James Version (KJV)
10:9 If thou confess with thy mouth - Even in time of persecution, when such a confession may send thee to the lions.
Ro 10:9 That if thou shalt confess with thy mouth the Lord Jesus. For the importance which Jesus attached to confession, see Mt 10:32 Lu 12:8 and compare Ac 8:37. To openly confess Christ in those days of persecution was a trial of faith of the severest kind. Note distinctly that there is no promise here to a concealed faith. And shalt believe in thine heart. That is, with all the heart. The belief must not be only a mental assent, but a belief that brings the whole man into loving trust and obedience to Christ. Such a faith is referred to in Ro 1:5 where the "obedience of faith" is described. Thou shalt be saved. Such a faith confessed unites its subject to Christ as his loving subject, and imparts to him the righteousness of those who have died to sin and been freed from the law. See Ro 6:1-4.